Equipments of this type, commercially known as double cutters, are used in systems for automatic processing documents, which have been previously printed on continuous forms.
The double cutters can operate, “on-line”, downstream from longitudinally cutting equipment, known as “merger” that divide the basic continuous forms in a longitudinal direction.
The double cutters of known type drive forward the continuous forms simultaneously or alternately and provide to separate, by means of a single blade, the printed sheets singularly or overlapped for the formation of the documents and following processings. For reason of cost and operational flexibility, cutting devices with alternative movements, for instance with guillotine blades, are used which require the stopping of the continuous form at the time of the cutting.
The operating velocity of the cutters on the market is conditioned by the velocity of the cutting device and the stresses to which are subjected the continuous forms entering in the equipment. Particularly good results have been obtained with the cutting equipment of the Italian Patent No. 1,360,399 in the name of Tecnau S.r.l. That equipment provides additional loops upstream of the cutting device and averaged velocities of the continuous forms at the inputs of the equipment. This allowed to reach the limit determined by the cutting device for the separation of the overlapping sheets. However, the overall productivity is lower than the theoretical productivity, when one of the continuous forms should be arrested for the production of documents with an odd number of sheets or for particular arrangements of the documents in undivided form. Further, the different velocities of the continuous forms, after the longitudinal separation by the “merger”, makes more difficult the standardization of the velocity of the continuous forms at the input of the equipment.
A transversal cutting equipment for sheets separable from overlapped continuous forms is the subject of the Italian Patent IT 1.397.442, also in the name of Tecnau S.r.l: The equipment of IT 1.397.442 comprises a cutting device, which can be activated for the simultaneous separation of the sheets from the continuous forms and a singularizing device of overlapped sheets for solving problems concerning documents with an odd number of sheets. In a specific embodiment, the singularizing device comprises a separating mechanism of the overlapped forms, having suction rollers downstream of the cutting device, two transport paths lying one above the other downstream of the suction rollers and an accumulating and forwarding device. The cutting device operates in continuous mode on the overlapped forms, while the transport paths can transport the sheets with differentiated velocities. This allows that a cut sheet of a following document, other than the document in formation, is transferred to the accumulating and forwarding device for the formation of the new document, substantially after the forwarding of the previous document. The devices achieved in accordance with this patent are fast, even in the case of documents having a reduced and odd number of sheets, but result quite expensive.